c# - How can I maintain a few mostly identical software products but based on the same codebase? -

please bear me , let me explain. work vehicle insurance company , trying develop online portal our customers can purchase insurance policies. let's offer 3 insurance products car insurance (ci), motorcycle insurance (mi) , truck insurance (ti). , shall 90% of these products similar in terms of how implement them differ in remaining 10%.

let me use c# example demonstrate (below code rough idea demonstrate problem not real code).

public class carinsurancepolicy {     //common properties among 3 insurance products     public decimal madeyear {get;set}     public decimal purcahseprice {get;set}      //specific particular product     public bool hascentrallocking {get;set}     public datetime specialdatetodowithcar {get;set} }  public class motorcycleinsurancepolicy {     //common properties among 3 insurance products     public decimal madeyear {get;set}     public decimal purcahseprice {get;set}      //specific particular product     public int enginestroke {get;set}     public datetime specialdatetodowithmotorcycle {get;set} }  public class truckinsurancepolicy {     //common properties among 3 insurance products     public decimal madeyear {get;set}     public decimal purcahseprice {get;set}      //specific particular product     public decimal loadcapacityintons {get;set}     public datetime specialdatetodowithtruck {get;set} } 

as can see each of policy class have properties same quite different each type. , comes database part.

i don't know if should this

create table baseinsurancepolicy (   //all common columns )  create table carinsurancepolicy (   //specific type of product )  create table motorcycleinsurancepolicy (   //specific type of product )  create table truckinsurancepolicy (   //specific type of product ) 

or should this

create table giantinsurancepolicytable (   //all columns , nullable ) 

and comes workflow part

we have few basic common steps rate type of product. take account of made year, km travelled etc form basic rating , depending on specific type of product , have special way calculate premium.

public class ratingengingforcar {    //can common step    public decimal getpremium() {}     //specific car    private void applya() {}    private void applyc() {} }  public class ratingengingformotorcycle {    //can common step    public decimal getpremium() {}     //specific motorcycle    private void applye() {}    private void applyf() {} }  public class ratingengingfortruck {    //can common step    public decimal getpremium() {}     //specific motorcycle    private void applyx() {}    private void applyz() {} } 

then have workflows again 90% similar 10% differ quite significantly. again it'll same generating insurance policy (the actual policy doc) , invoices.

so don't know if whether should come kind of generic yet flexible way form base classes , start inheriting , modifying specific behaviour each product. or should copy past 1st product , modify 2,3,4,5 products?

in terms of ui, trying componentize our javascript in general long html structure same , id/name/class functionality provided *automatically including , initiating js. trouble need duplicate html everywhere every products.

i don't know if i've explained problem clear enough high level. if not update / clarify based on comments. thank much.

on code side, problem object orientation there solve. put common functionality in base class , derive more specialised classes that.

you can similar thing in database. example, have policy table column each of common properties plus id. can have specialist tables containing other fields (e.g. 1 table car insurance) column that's foreign key reference base table.

you add view database presents these if 1 giant table, haven't lost structuring nicely.